Structures for probing small pads in close proximity have been known and are in common use, however, due to inherent problems of maintaining conformance and limiting the background noise and cost constraints, prior art has not, as yet, filled the need for combination high and low frequency shielded probe cards in the still advancing technology of microelectronic circuits.
A search of the prior art did not disclose any patents that read directly on the claims of the instant invention, however, the following U.S. patents were considered related:
______________________________________ Patent No. Inventor Issue Date ______________________________________ 4,065,717 Katter et al Dec. 27, 1977 4,063,172 Faure et al Dec. 13, 1977 4,061,969 Dean Dec. 6, 1977 4,045,737 Coberly Aug. 30, 1977 3,906,363 Fowler Sep. 16, 1975 3,869,698 Beltz Feb. 18, 1975 3,560,907 Heller Feb. 2, 1971 ______________________________________
Katter et al teaches a plurality of leads on a backing plate that is transparent and resilient. The ends of the leads are provided with raised portions which establish the probes, preferably formed by conventional thin film or plating techniques. A vacuum is pulled on the chip under test firmly securing it in place while pressure is applied above the resilient backing plate causing deformation to occur, moving the probes into contact with the workpiece.
Faure et al apply a group of probes for multiple site chip clusters with a plurality of cams cooperating with followers to independently locate each cluster or groups of probes so as to compensate for accumulated tolerance or shrinkage in long substrates. Clusters of probes are moved with a single adjustment laterally, as a group, with the probes taking advantage of the collapsing column or buckling beam configuration for compliance.
Dean employs a series of pins embedded into a sealed flexible membrane with wires attached to the pins passing through an airtight seal. A vacuum is pulled within a chamber formed by the membrane causing the pins to obtain conformance with the workpiece under this negative pneumatic pressure. Dean also takes advantage of the previously described spring loaded probes in another embodiment.
Coberly discloses a plastic substrate provided with a groove in which an electrically conductive contact or probe is positioned within a key portion. The probe contains a pair of cantilevers which bias against the edge of the substrate providing a planarity stop serving as vertical alignment. The bias produced by the cantilevers is overcome and a flat raises upwardly from the edge of the substrate as the point touches the chip. The electrical conductive flowpath is continued from the probe via a wire lead to a binding post and, hence, to collateral test apparatus.
Fowler teaches a wire positioned between two plates with one end restrained and the other slideably engaged. The moveable end projects through the plate and contacts the element under test. The wire or needle deforms within its elastic limits, as a collapsing column when pressed onto the node points of the workpiece. The expense of drilling two corresponding plates is high and the needles have a tendency to run into each other when depressed, limiting the reliability of thrs art.
Beltz et al discloses a plurality of leads simultaneously bent into a truncated shape. The probe fingers are an extension of the lead, as above, but are formed at the same time with a conventional die set after the leads are secured in a plastic material. The fingers or probe tips are separated by severing with a sharp instrument. Further, the leads may be lapped to impart to them the desired degree of flatness and smoothness, as to not damage the semiconductor beam leads on which they rest during probing.
While the prior art addresses the problem of compliance and provides an electrical flowpath for frequencies up to 1.0 megahertz using conventional wires and conductive structure, it is still lacking in structure that is capable of conveying both low and high frequency signals as separate means to conduct each signal together. Further, no allowance has been given to shield the measuring device from unwanted RFI and EMI simultaneously.
For background purposes and as indicative of the art to which the invention relates, reference may be made to the remaining cited patents.